The present invention relates to a method of manufacturing a gas flow type sensor which is used for detecting an angular velocity or an acceleration acting on a sensor body by using a pair of heat wires for sensing a deflection of the gas flow in a gas path of a sensor body when the above-mentioned angular velocity or acceleration is applied on the sensor body.
Recently, as known from Japanese Laid-Open Patent Publication No. 58-56476, such a gas flow type sensor has been developed that has a body comprising a gas path and a pair of heat-wires bridged over the gas path and that is manufactured by semiconductor micro-machining on the basis of IC technology.
In this type sensor, the body portion is constructed of two semiconductor substrates: the lower substrate on which silicon nitride (SiN), platinum (Pt) and silicon nitride (SiN) are sequentially deposited in three layers, a heat-wire bridge is formed by pattern etching the three-layer portion and a half-groove is formed under the bridge by etching the semiconductor substrate, and an upper semiconductor substrate in which a half groove is formed by etching. The upper substrate is bonded to the lower substrate so as to precisely couple the half grooves to form the gas path with the heat-wire bridge.
In manufacturing the sensor, a three-layer coat is formed on the lower semiconductor substrate by sequentially depositing a first (bottom) layer of SiN by a chemical-vapor depositing (CVD) method, a second layer of Pt by a sputtering method and a third (top) layer of SiN by a CVD method. These different methods must be conducted in different working chambers. While the substrate after depositing thereon a SiN-layer in a CVD chamber is transferred to a Pt-sputtering chamber, it may be exposed to air, resulting in oxidization of the SiN-layer. Furthermore, the substrate may be subjected to oxidization of the SiN-layer with air contained in an atmosphere when sputtering the second Pt-layer in the sputtering chamber. The oxidation of the SiN-layer results in port adhesion with the Pt-layer. This may affect the performance of the sensor.
Accordingly, the prior art disclosed in Japan Laid-open Patent Publication No. 2-226017 proposes the provision of an interconnection layer between the SiN-layer and the Pt-layer to improve adhesion between the layers. This solution, however, requires the provision of an additional process of forming an interconnection layer between the working layers, thereby complicating the manufacture of the above-mentioned sensor body.